changed format of builtin shader strings to use comma separated lines,

changed format of builtin shader strings to use comma separated lines,
this should fix compilation on MSVC where default.glsl exceeded 65535
character limit
removed MODE_SHOWDEPTH from shaders and code because it is not used and
is not likely to ever be used anyway
reworked shadermodeinfo_t to only have one filename rather than separate
filenames for vertex and fragment shader
reworked r_glsl_dumpshader to cope with multiple shader filenames and
unified some code for glsl and hlsl text processing

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@11889 d7cf8633-e32d-0410-b094-e92efae38249